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| Book/Report | FZJ-2020-00793 |
2001
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/24156
Report No.: Juel-3870
Abstract: The interplay of magnetism, electronic structure and atomic geometry has been investigatedon fcc-Mn and fcc-Fe films and on Co quantum wires.An angle-resolved photoemission study of epitaxial fcc-Mn films shows that the Mnelectronic states lack a significant dispersion in sharp contrast to standard band theoryand other $\textit{3d}$ transition metals in fcc-structure. Dynamical mean field calculations findthat strong electron correlation effects largely suppress the band dispersion and providefirst evidence for the formation of Hubbard bands in pure transition metals.The magnetic properties of the epitaxial fcc-Fe films on Co(100) and sandwichedbetween two Co(100) films have been investigated by means of x-ray magnetic circulardichroism (XMCD). The dependence of the Fe magnetic behaviour on the film thicknessis complex and qualitatively similar on Co(100) and in fcc-Co/Fe/Co(100) trilayers. Forthe trilayer structure, an oscillatory coupling between the Co films mediated by fcc-Fefilms has been observed. Nuclear resonant scattering of synchrotron radiation providedatomic-layer-resolved information about the magnetic structure of the fcc-Co/Fe/Co(100)trilayer system. Our measurements disclose a non-collinear magnetic structure in the Fefilm.First insights into the electronic and magnetic properties of monatomic Co wires couldbe obtained with angle-resolved photoemission and XMCD. The Co wires have been preparedby step-edge decoration of the vicinal Pt(997) surface. In the photoemission measurements, they display a $\textit{3d}$ double-peak structure which indicates the presence of aone-dimensional exchange-split band and of local magnetic moments. Our XMCD measurementsreveal superparamagnetic behaviour of the monatomic Co wires and an orderingtemperature of T < 10 K. The Co wires display a uniaxial magnetic anisotropy and a preferentialorientation of the magnetic moments perpendicular to the wire axis. Increasingthe Co wire width, strong changes of the magnetic anisotropy have been observed. Bymeans of XMCD sum rules, an enhancement of the orbital moment by a factor of 4.8 hasbeen determined for the monatomic Co wires with respect to bulk Co.
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